This application takes priority from Korean Application No. 10-2001-0053162 filed Aug. 31, 2001.
1. Field of the Invention
The present invention relates to a key switch for use in an input device such as a keyboard of a PC (Personal Computer), and more particularly to a key switch which is intended to realize a compact and slim keyboard and to provide a high keystroke and a resilient click sense to a user by its simple configuration, thereby affording a reliable key-input performance. The present invention also relates to a key switch adapted to be produced by a simple manufacturing process.
2. Description of the Prior Art
These days, key tops have been thinned and flattened to comply with needs for compact keyboards, and a high keystroke and a reliable clear click sense are required to enhance ease and reliability of a key-input operation. There are proposed various key switches for use in such keyboards.
For example, Japanese Patent Laid-Open No. 8-279316 discloses a key switch described hereinafter.
A guide assembly for guiding an up-and-down motion of a key top is comprised of first and second link members. The first and second link members are hingedly connected in an xe2x80x9cUxe2x80x9d shape to guide the vertical motion of the key top. The first link member is provided at its end with a spring member having a switch-actuating portion, and a support plate is provided with a slanted protrusion having an inclined face. As the spring member is slid on the inclined face of the slanted protrusion, a resistance to movement of the spring member is gradually increased. When the spring member is slid beyond the peak of the slanted protrusion and then comes into contact with a switch seat, the resistance to movement of the spring member is suddenly reduced, thereby affording a click sense to a user. At the same time, the switch actuation portion of the spring member presses a switching portion.
Since the key switch is adapted to employ the guide assembly comprised of a link mechanism rather than a rubber spring, it is possible to realize a compact and slim keyboard. Furthermore, since the switch-actuating portion of the spring member is slid beyond the slanted protrusion, thereby providing a variation of the resistance, a user can feel a clear click sense.
However, there is a limit to realization of a slim keyboard by such a known link mechanism. More specifically, it is impossible to reduce a thickness of a keyboard to a value not greater than a stroke length of the key top because a click sense (or a touch sense) becomes poor owing to reduction of a stroke length of the key top. Accordingly, it is necessary to reduce thickness of components other than a stroke length of the key top. In addition, it is required to reduce a thickness of a keyboard to a value not greater than a stroke length and for a user to have the keyboard in his custody when the keyboard is not used.
In addition, as notebook computers and PDAs are extensively distributed, more compact key switches are required.
Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a key switch which is adapted to raise or lower a key top by its stroke length, according to whether a keyboard is used or not, thereby affording a favorable click sense and a reduction of thickness of a notebook or a PDA.
In order to accomplish the above object, the present invention provides a key switch comprising: a key top which is pressed down by a user""s finger; a link assembly comprised of first and second link members, which is lowered by pressure of the key top and is raised together with the key top by release on the pressure of the key top, the first link member including two legs pivotably connected to the key top at their upper ends, and a strip-shaped elastic member positioned between the both legs which is adapted to raise the first link member by application of an external force, the second link member including two legs pivotably connected to the key top at their upper ends and pivotably connected to a frame of a keyboard at their lower ends, the first and second link members being provided at their center portions with a hinge means comprised of a hinge protrusion and a hinge hole to allow the link assembly to be extended and retracted; an FPC (Flexible Printed Circuit) placed on the frame of the keyboard, which enables a character printed on the key top to be recognized by a contact between the link assembly and the FPC when the link assembly is lowered; and a plate placed on the FPC to be moved with respect to the frame of the keyboard, to which lower ends of the legs of the first link member are pivotably connected, and which is provided with an elastic supporting member for applying elasticity to the elastic member of the first link member when the plate is moved in a direction; whereby, when the key top is applied with pressure, the link assembly is retracted and lowered while overcoming an elasticity of the elastic supporting member of the plate, and when the link assembly is further lowered, an elastic resistance of the elastic supporting member is suddenly increased, and thus the elastic member of the first link member is suddenly bent into a bow shape and quickly lowered, thereby affording a click sense to a user and enabling the bent portion of the elastic member to press the FPC to recognize a signal corresponding to the key top.